Method for manufacturing semiconductor device

Abstract

A highly reliable semiconductor device including an oxide semiconductor film with high crystallinity is provided. A first oxide semiconductor film and a second oxide semiconductor film are stacked over an insulating layer. After forming source and drain electrode layers on the second oxide semiconductor film, a third oxide semiconductor film is provided in contact with the second oxide semiconductor film and top surfaces and the source and drain electrode layers. At least one of the first, second, and third oxide semiconductor films is an oxide semiconductor film having a single crystal region.

What is claimed is: 
     
       1. A method for manufacturing a semiconductor device comprising the steps of:
 forming a first insulating layer; 
 forming a first oxide semiconductor layer over the first insulating layer; 
 forming a second oxide semiconductor layer over the first oxide semiconductor layer; 
 forming a source electrode layer and a drain electrode layer on and in contact with the second oxide semiconductor layer; and 
 forming a third oxide semiconductor layer on and in contact with the second oxide semiconductor layer, the source electrode layer, and the drain electrode layer, 
 wherein at least one of the first, second, and third oxide semiconductor layers comprises a single crystal region having a crystal structure, and 
 wherein the crystal structure of the single crystal region has bonds for forming a hexagonal lattice in an a-b plane of the crystal structure and includes a c-axis perpendicular to a surface of the first insulating layer. 
 
     
     
       2. The method for manufacturing a semiconductor device according to  claim 1 , wherein the first insulating layer comprises one of silicon oxide, silicon oxynitride, and silicon nitride oxide. 
     
     
       3. The method for manufacturing a semiconductor device according to  claim 1 , wherein the third oxide semiconductor layer covers side surfaces of the source electrode layer and the drain electrode layer. 
     
     
       4. The method for manufacturing a semiconductor device according to  claim 1 , wherein at least one of the first, second, and third oxide semiconductor layers comprises indium, gallium, and zinc. 
     
     
       5. The method for manufacturing a semiconductor device according to  claim 1 , wherein at least one of the first, second, and third oxide semiconductor layers is formed by a film formation method comprising steps of:
 preparing a sputtering target including a polycrystalline oxide containing a plurality of crystal grains; 
 forming a plasma space containing an ionized gas, in contact with a surface of the sputtering target and a surface to be deposited; 
 separating a plurality of flat plate-like sputtered particles each having a hexagonal shape from a cleavage plane of the plurality of crystal grains by collision of ions of the ionized gas with the surface of the sputtering target; 
 moving the plurality of flat plate-like sputtered particles on the surface to be deposited, each flat plate-like sputtered particle positively or negatively charged along sides of the hexagonal shape; and 
 arranging the plurality of flat plate-like sputtered particles so that one side of the hexagonal shape of a first flat plate-like sputtered particle and one side of the hexagonal shape of a second flat plate-like sputtered particle adjacent to the first flat plate-like sputtered particle are in contact with each other. 
 
     
     
       6. The method for manufacturing a semiconductor device according to  claim 5 , wherein the ionized gas is selected from the group consisting of a gas containing oxygen, a gas containing a rare gas element, and a gas containing oxygen and a rare gas element. 
     
     
       7. A method for manufacturing a semiconductor device comprising the steps of:
 forming a first insulating layer; 
 forming a first oxide semiconductor layer over the first insulating layer; 
 forming a second oxide semiconductor layer over the first oxide semiconductor layer; 
 forming a source electrode layer and a drain electrode layer on and in contact with the second oxide semiconductor layer; 
 forming a third oxide semiconductor layer on and in contact with upper surfaces of the second oxide semiconductor layer, the source electrode layer, and the drain electrode layer, wherein the third oxide semiconductor layer covers side surfaces of the source electrode layer and the drain electrode layer; 
 forming a second insulating layer over the source electrode layer, the drain electrode layer, and the third oxide semiconductor layer, 
 wherein at least one of the first, second, and third oxide semiconductor layers comprises a single crystal region having a crystal structure, and 
 wherein the crystal structure of the single crystal region has bonds for forming a hexagonal lattice in an a-b plane and includes a c-axis perpendicular to a surface of the first insulating layer. 
 
     
     
       8. The method for manufacturing a semiconductor device according to  claim 7 , wherein the first insulating layer comprises one of silicon oxide, silicon oxynitride, and silicon nitride oxide. 
     
     
       9. The method for manufacturing a semiconductor device according to  claim 7 , wherein at least one of the first, second, and third oxide semiconductor layers comprises indium, gallium, and zinc. 
     
     
       10. The method for manufacturing a semiconductor device according to  claim 7 , wherein at least one of the first, second, and third oxide semiconductor layers is formed by a film formation method comprising steps of:
 preparing a sputtering target including a polycrystalline oxide containing a plurality of crystal grains; 
 forming a plasma space containing an ionized gas, in contact with a surface of the sputtering target and a surface to be deposited; 
 separating a plurality of flat plate-like sputtered particles each having a hexagonal shape from a cleavage plane of the plurality of crystal grains by collision of ions of the ionized gas with the surface of the sputtering target; 
 moving the plurality of flat plate-like sputtered particles on the surface to be deposited, each flat plate-like sputtered particle positively or negatively charged along sides of the hexagonal shape; and 
 arranging the plurality of flat plate-like sputtered particles so that one side of the hexagonal shape of a first flat plate-like sputtered particle and one side of the hexagonal shape of a second flat plate-like sputtered particle adjacent to the first flat plate-like sputtered particle are in contact with each other. 
 
     
     
       11. The method for manufacturing a semiconductor device according to  claim 10 , wherein the ionized gas is selected from the group consisting of a gas containing oxygen, a gas containing a rare gas element, and a gas containing oxygen and a rare gas element.